The invention relates to calenders and like machines for the treatment of running webs of paper, textile material or the like. More particularly, the invention relates to improvements in guards for the inlet sides of nips of pairs of rolls which are used in calenders and like machines. Still more particularly, the invention relates to improvements in guards of the type disclosed in commonly owned U.S. patent application Ser. No. 205,082 filed June 9, 1988 by Egon Hutter et al. for "Guard for the nips of rolls in calenders", now U.S. Pat. No. 4,867,055 granted Sept. 19, 1989.
The application of Hutter et al. discloses a guard wherein an elongated hollow support extends longitudinally of the inlet side of the nip of two rolls. The support is mounted in the frame of the machine and carries two elongated strip-shaped blocking devices each closely adjacent one of the rolls which define the nip. The blocking devices comprise sets of individually movable sections, and the support carries devices which can move individual sections relative to the respective roll as well as relative to other sections of the respective blocking device. The devices for moving the sections of the two blocking devices include motion transmitting rods which extend through the support. The purpose of multi-section adjustable blocking devices is to ensure that the width of the clearance between a blocking device and the adjacent roll does not exceed a value (e.g., 8 millimeters) which is prescribed by authorities and/or by labor unions in order to reduce the likelihood of injury to the hand of a careless operator. Adjustability of sections of the blocking device with reference to the adjacent rolls is necessary because the width of the aforementioned clearances between the rolls and the respective blocking devices often varies as a result of flexing of the rolls and/or of the carrier, as a result of thermally induced expansion or contraction of parts in the region of the nip, reduction of the diameters of the rolls and/or for other reasons.
It is already known to discharge a fluid against the rolls and/or against the running web in a calender or a like machine. As a rule, fluid is applied along the full length of the nip. For example, published German patent application No. 35 03 448 of Hanhikoski et al. discloses means for directing steam against the running web. Analogous steam directing means are disclosed in German Auslegeschrift No. 1 295 993 of Muller. U.S. Pat. No. 2,993,432 to Youngchild discloses an apparatus for heating or cooling calender rolls with hot or cold air. It is further known to provide fluid blowing tubes along the nips of rolls in calenders and like machines. In each instance, a device which defines an elongated fluid-conveying channel must be placed adjacent the inlet side of the nip of two rolls, and such channel-defining device is formed with one or more rows of fluid discharging orifices which direct streams or jets of a fluid medium toward the nip or toward the running web.
A drawback of conventional apparatus of the above outlined character is that they occupy a substantial amount of space, for example, at the inlet sides of the nips of pairs of rolls in calenders and like machines. This renders it necessary to increase the distance between successive nips which, in turn, can affect the stability or treatment of the running web and the quality of the finished web. Still further, a pipe or another device which is used solely as a means for directing fluid against the roll or rolls and/or against the running web in a calender or a like machine must be provided in addition to a guard; this creates serious problems due to crowding of numerous parts at the inlet sides of the nips.